CeO2–Ni carbon nanofibers for electrochemical ammonia conversion from wastewater into power in membrane-less fuel cells

• Electrospun CeO 2 –Ni CNFs were synthesized and optimized for ammonia electrooxidation. • The 10 wt% CeAc catalyst exhibited superior activity with low activation energy. • A high electrochemically active surface area of 2600 cm 2 /g was achieved. • DAFC testing showed a maximum power density of 138.2 mW/m 2 using the optimized anode. • The study offers a sustainable approach for energy recovery from ammonia-containing waste. The increasing demand for sustainable energy solutions has driven the search for efficient electrocatalysts capable of recovering energy from industrial waste streams. In this study, electrospun CeO 2 –Ni-incorporated carbon nanofibers were synthesized and evaluated as advanced anodes for ammonia electrooxidation in both three-electrode systems and membrane-less direct ammonia fuel cells (DAFCs). The structural and morphological characteristics of the nanofibers were confirmed by XRD, SEM, and TEM, revealing well-dispersed Ni and CeO 2 nanoparticles embedded within a conductive fibrous carbon matrix. Electrochemical investigations demonstrated that the optimized electrode with 13 wt% CeAc exhibited the highest electrocatalytic activity, with a maximum current density of 60 mA/cm 2 in 1.0 M KOH containing 1.0 M ammonia. Reaction kinetics analysis revealed an apparent activation energy of 37.4 kJ/mol, and a calculated electrochemically active surface area (ECSA) of 2600 cm²/g. Statistical modeling using Design-Expert® confirmed the significance of ammonia concentration and CeAc content on both current density (F = 10.23, p < 0.0001) and peak potential (F = 30.24, p < 0.0001). When implemented in DAFCs, the 10 wt% electrode achieved a maximum power density of 138.2 mW/m 2 at 2.0 M ammonia, outperforming the 9 wt% and 13 wt% counterparts. Interestingly, elevated temperatures negatively affected the DAFC performance, with power density decreasing from 188.7 to 82.6 mW/m 2 for the 5 wt% electrode between 35–65 °C, highlighting the impact of ammonia volatility and system limitations. Overall, the results demonstrate that CeO 2 synergistically enhances Ni-based electrocatalysis, while the nanofibrous architecture enables efficient charge transfer and fuel accessibility.